As is well known, wireless telephones are identified by two pieces of information: the mobile identification number (MIN) and the electronic serial number (ESN). This information may be obtained and placed in another wireless telephone for the illicit purpose of making calls that will be billed to the person to whom the MIN and ESN were legitimately assigned. The MIN and ESN information is easily obtained because it is broadcast over the "air interface" between the wireless telephone and a wireless carrier's mobile switching center (MSC), and is, therefore, subject to capture via specialized scanning equipment that is readily available to thieves. This type of theft of services (known as "cloning") both inconveniences the customer and results in losses to the wireless carrier.
One prior art proposed solution is to monitor the calling patterns for all wireless calls, on a per customer basis, and to block any calls that do not correspond to the customer's prior calling pattern. This solution suffers from the problems that 1) it may result in the blocking of calls for an authorized customer if they change their calling pattern, 2) it will not successfully block calls from phones that continually change the MIN-ESN that they use (so-called "tumbler-cloner" or "magic phones"), and 3) typically the calling pattern can only be checked after the call is completed, at which time it is too late to prevent the fraud.
Another proposed prior art solution is to utilize the IS 54 B Cellular System Dual-Mode Mobile Station--Base Station Compatibility Standard (Rev-B). The IS 54 B standard calls for pre-call authentication of the calling wireless telephone using a "shared secret key" over a digital call set-up channel. A shared secret key is a key that is known only by the two parties involved in the authentication. However, this proposed solution suffers from the problems that in order to be operative it requires both 1) cooperation and investment on the part of all the wireless carriers, in particular a) the ability to access each other's data bases where the keys are stored and b) upgrading of their switching equipment to be compatible with the IS 54 B call setup standard; and 2) upgrading of the 10 million wireless telephones that are already in existence to handle call setup according to the IS 54 B standard. These propositions are both expensive and not likely to happen in a short time frame.